The present disclosure broadly relates to printing systems and, more particularly, to a media tray, printing system and method of operation for improved media size and/or orientation detection.
Known printing systems are generally capable of marking sheets of media of a variety of types (e.g., plain paper, bond paper, recycled paper, card stock, transparencies), sizes (e.g., letter, legal, A3, A4) and/or in different orientations (e.g., long-edge feed, short-edge feed). Typically, a known printing system will include at least one media tray capable of receiving a bulk quantity (e.g., stack, package, ream) of sheets of media and introducing the bulk quantity to a suitable sheet feeding system or mechanism to advance individual sheets in an known manner. Often, known printing systems will include numerous media trays with each tray receiving a different type, size and/or orientation of sheet media.
Many known printing systems are capable of determining which particular one of a number of pre-defined sizes and/or orientations of sheet media have been loaded into the storage tray. Unfortunately, these and other known printing systems and media tray arrangements suffer from problems and disadvantages that can, in certain applications, limit the use and/or effectiveness of the same.
One such problem is that known systems are typically only capable of detecting a minimal number of sizes and/or orientations of sheets of media. This can be due to the operational strategy that is used and/or the components or arrangement thereof that is used by the sensing system.
Known operational strategies that are commonly used for size and/or orientation detection include sensing only one direction (e.g., width dimension only, length dimension only) and sensing in two directions (e.g., both length and width dimensions). Clear disadvantages exist with strategies that detect only one dimension, as sheet media with identical edge dimensions cannot be differentiated. For example, a printing system that only receives a sensor signal indicating that the loaded sheet media has an 11 inch dimension would not, without more information, be able to distinguish between 8-½ inch×11 inch media oriented long-edge first and 11 inch×17 inch media oriented short-edge first.
Due to the substantial disadvantages single direction sensing systems, many known printing systems detect two dimensions of loaded sheets (e.g., media length and media width). One example of such a known printing system is disclosed in U.S. Pat. No. 5,333,852 to Millilo et al. (hereinafter Millilo), which utilizes five different switches to detect the size and/or orientation of the loaded sheet media. One switch (S1 in FIG. 7 of Millilo) is dedicated to sensing the presence or absence of the sheet media tray within the printing system. Such switches are commonly referred to “tray home” switches, which generate a signal indicating that the associated media tray is received within the printing system in a “home” position. Another switch (S5 in FIG. 7 of Millilo) senses the “width” dimension of the loaded media, and its switch state depends upon the position of the “width” guide within the media tray. The remaining three switches (S2-S4 in FIG. 7 of Millilo) detect the “length” dimension of the loaded media. An actuator arm includes several actuators or projections that selectively engage switches S2-S4 depending upon the position of the actuator arm, which is connected to the “length” guide within the tray. The arrangement in Millilo, as well as other known arrangements, permits the printing system to automatically detect the size of the loaded media based upon the combined condition or operational state (e.g., open or closed) of the switches.
One disadvantage of known arrangements, such as that disclosed in Millilo, for example, is that selectively actuating the given number of switches in such a manner permits only limited number of switch combinations. Therefore, only a limited number of media sizes and/or orientations can be detected. For example, Millilo discloses the detection of about 7 different media sizes and/or orientations using the arrangement disclosed therein. However, as printing systems become increasingly sophisticated, it is commonly desirable for printing systems to recognize a greater variety of media sizes and/or orientations. It will be recognized that a greater number of media sizes and/or orientations could be detected by the arrangement in Millilo if a greater number of switches were to be used. However, the use of a greater number of switches would be likely to undesirably increase production costs. Additionally, such a modification would also be likely to generate design and/or assembly issues due to the increased usage of space within the printing system.
Other known arrangements utilize sensing systems similar to that disclosed in Millilo. However, such other known systems avoid the use of a dedicated switch for determining the presence or absence of the media tray (i.e., a “tray home” switch), and instead utilize that switch as a fourth “length” switch. This permits an increased number of media sizes and/or orientations to be detected. For example, FIG. 13 illustrates a media size and orientation matrix having columns 1 through 9 extending along the bottom of the chart representing known length dimensions and rows A through G extending along the left side representing known width dimensions. A row extends across the top of the chart and includes a representative condition or state of the four length switches (e.g., 0111, 1011, 1001, 1110, 0101, 1000, 0011, 0010 and 1100), with a “0” representing an open switch and a “1” representing a closed switch. A column extends along the right side of the chart and includes representative conditions of the single width switch (e.g., 0 or 1). Generally, then, a size and/or orientation of a sheet of media can be determined based upon the combined conditions or states of the length and width switches using the arrangement W1L1L2L3L4 in which the “W” represents the width switch state and each “L” represents a length switch state.
As an example, a media length of 210 mm is represented in column 1 by the length switch state 0111. A media width of 148.5 mm is represented in row B by the width switch state 0. A sheet of media having a width of 148.5 mm and a length of 210 mm is more commonly referred to A5 sized media, which would be oriented to feed short-edge first (SEF), and would be addressed in the chart by combined switch state 00111. As another example, a media length of 355.6 mm is represented in column 7 by length switch state 0011, and a media width of 215.9 mm is represented in row E by switch state 1. A sheet of media having such length and width dimensions would more commonly be referred to as Legal sized media, which would be oriented to feed short-edge first (SEF), and would be addressed in the chart by combined switch state 10011.
Using a sensing arrangement and strategy such as that shown in FIG. 13, known printing systems can identify an increased number of pre-defined sheet media sizes and orientations over earlier systems, such as that in Millilo, for example, due to the additional length switch that is available. As an example, FIG. 13 identifies 11 different sizes and/or orientations of sheet media in bold characters. However, these systems and arrangements also include problems and disadvantages that can limit the application and/or use thereof.
One example of such an issue will be recognized from FIG. 13, in which rows A-C of each column are represented by the same combined switch state. Similarly, rows D-G of each column are also represented by the same combined switch state. As an example, sheet media referred to as Executive sized media oriented to feed short-edge first is shown in box 3C as being addressed by combined switch state 01001. As such, a printing system receiving an electrical or other signal representing this combined switch state would identify the media within the tray as being Executive sized media oriented to feed short-edge first within the tray. However, sheet media having a length of 266.7 mm (column 3) and a width of 139.7 mm (row A) or 148.5 mm (row B), would also return a combined switch state of 01001. As a result, such sheet media would be misidentified by the printing system as being Executive sized media, even though it would be of a substantially different width than Executive sized media. In FIG. 13, there are 16 occurrences of a smaller sheet of media being identified as a larger sheet of media. These occurrences are indicated by a heavy or bold lined border, and include boxes 1A, 1D-F, 2D-E, 3A-B, 4D, 6D, 7D, 8D-F, and 9D-E. Additionally, there are 14 occurrences of a larger sheet of media being identified as a smaller sheet of media. These occurrences are indicated in FIG. 13 by a double lined border, and include boxes 1C, 2B-C, 2G, 4F-G, 5E-G, 6F-G, 7F-G and 9G.
While it is desirable to minimize both types of occurrences of misidentification, the misidentification of a smaller sheet of media as being a larger sheet of media may be more problematic in some applications than in others. One example of an application in which is desirable to maximize the number of recognized media sizes and/or orientations and minimize detections of smaller sheet of media as larger sheets involves printing systems, such as those that utilize ink or toner as a marking substance, for example. Typically, such printing systems apply the ink or toner to a rotating drum before the marking substance is transferred onto a passing sheet of media. It will be recognized, however, that ink and toner cannot readily be removed from the rotating drum other than by applying the ink to a passing sheet of media. As such, it is beneficial to avoid the application of a marking substance along the rotating drum outside the extents of the sheet of media, as the ink or toner that is not transferred to the passing sheet of media will remain on the drum. Repeated occurrences of such an event could have undesirable effects on output quality and/or the components themselves.